Like most of you, I assumed the tip was the only part that fired, considering the blast marks from the exhaust. And yes, looks like an RPG to me too. I saw in the Fett/Jodo comic though that they fired the missile like in ATOC, which disappointed me. And then in AOTC, disappointed me even further. The best explanation I can come up with is that the made it the whole thing so it would be easier for the audience to see it, and thus tell what's happening. Who knows though... and of course, yeah, like every other discrepency between Jango's and Boba's costumes, this could be chalked up to "boba probably changed it in the 20 years between the movies".